A liquid crystal display (LCD) panel is mainly colorized by a color filter. The liquid crystal (LC) molecules, which are arranged in rows or twists by changing the voltage of the driver integrated circuit (IC), can form gates to determine whether a backlight can pass through the LC molecules or not, so as to generate pictures on the LCD panel. However, the LCD panel shows only two colors in black or white due to the difference in levels of the light penetration. If the LCD panel is to show colors, it needs a combination of three light sources of red (R), green (G), and blue (B). Hence, a color filter with three colored layers of red, green, and blue is a key component of the LCD panel.
Reference is made to FIG. 1, which illustrates a cross-sectional diagram showing a color filter in the prior art. The color filter 100 comprises a transparent substrate 100 made of, for example, glass. A black matrix 103 is disposed on the transparent substrate 101. The black matrix 103 is used as a light-shielding, anti-reflection layer to avoid color mixing and color contrast enhancement. A plurality of apertures 105 is located in the black matrix 103 to expose a part of the transparent substrate 101. The colored layers 107 of transparent red, green, and blue are formed in the apertures 105, respectively. The colored layers 107 are covered with a protective layer 109 and a transparent ITO (Indium-Tin Oxide) conductive film 111 in turn.
The color filter usually has properties of high color purity, high transparency, high contrast, low reflectivity, and must be stably resistant to heat, light and chemicals. There are currently are four common methods of coating the colored layers on the color filter, a dyeing method, a pigment dispersion method, an electro-deposition method, and a printing method. However, the above methods require complicated processes and expensive equipment, and have limitations regarding the size of the color filter. In addition, the increase in processes and the size causes the yield to be decreased, and results in wasting a great quantity of material and increasing the cost of the production. To solve the problems of fabricating the colored layers of the foregoing color filter, the ink-jet technique has been recently developed to reduce the consumption of negative photoresists as well as steps of exposure and development.
The ink-jet technique is excellent because it uses small-sized equipment, less process time and less ink. Generally, the ink-jet technique is divided into Piezoelectric ink-jet and thermal bubble ink-jet methods, and it may replace the conventional method of fabricating the color filter in the future. However, the ink-jet technique is applied to produce the colored layer of the color, and the colored ink drops with enhanced diffusibility when injected into the apertures of the black matrix may overflow even to result in color mixing and color contrast deterioration.
Reference is made to FIGS. 2(a) to 2(c), which illustrate cross-sectional diagrams of the process of the color filter in the prior art. The process may be a method of manufacturing the color filter disclosed in the U.S. Pat. No. 6,399,257. A photosensitive resin 141 is formed on the transparent substrate 131 and the apertures 135 of the black matrix 133, as shown in FIG. 2(a). Next, a step of backside exposure is performed, in which an exposed region of the photosensitive resin 141 becomes an ink-absorbent layer 145 and an unexposed region becomes an ink-repellent layer 147, as shown in the structure of FIG. 2(b). Subsequently, colored ink drops are injected into the apertures 135 of the black matrix 133 by the ink-jet technique, and then a colored layer 149 is formed, as shown in the structure of FIG. 2(c). The aforementioned ink-repellent layer 147 can separate the portions of colored layer 149 from each other, thus can reduce the problem of the colored ink drops overflowing.
Reference is made to FIGS. 3(a) to 3(c), which illustrate cross-sectional diagrams of the process of another color filter in the prior art. The process may be a color filter and method of manufacturing the same disclosed in the E. P. Pat. No. 1,061,383. An organic photosensitive film 155 is applied on the transparent substrate 151 and the black matrix 153, as shown in the structure of FIG. 3(a). Next, steps of exposure and development are performed, and a plurality of apertures 157 is formed in the photosensitive film 155 and the black matrix 153 to expose a part of the transparent substrate 151, as shown in the structure of FIG. 3(b). The organic photosensitive film 155 is used as an ink-repellent layer. Subsequently, colored ink drops are injected into the apertures 157 of the black matrix 153 by the ink-jet technique, and then a colored layer 159 is formed as shown in the structure of FIG. 2(c). The aforementioned organic photosensitive film 155 is used as the ink-repellent layer to separate the portions of colored layer 159 from each other, thus can reduce the problem of the colored ink drops overflowing.
In brief, the prior solution directed to the problem of the colored ink drops overflowing mainly focuses on changing the surface property of the black matrix. In other words, the problem of the colored ink drops overflowing is improved by adding the ink-repellent layer on the black matrix. However, the cost of fabricating the ink-repellent layer is higher. It is necessary to coat more the ink-repellent layer uniformly over the transparent substrate and the black matrix. Furthermore, the ink-repellent layer must be formed from steps of exposure and development.